The construction of a unitized vehicle body commences with the formation of individual major body panels by stamping the panels from sheet metal blanks. Typically, these major panels include a floor panel, right and left body side panels, a fire wall and either a roof panel or transversely extending inner members to which a roof panel is subsequently mounted. After the individual panels are stamped, some preliminary assembly operations can then be performed on the individual panels such as for example adding door hinge and latch hardware to body side panels at appropriate locations proximate the door opening, adding seat mounting brackets and reinforcements to the floor panels, etc.
Next a set of panels that together constitute a sub-assembly of the finished vehicle body is loosely assembled together. This initial loose assembly of panels frequently is accomplished by a “toy tab” arrangement in which one or more panels is formed with a tab which projects from an edge and which is received in a slot in an adjacent panel. This technique interlocks the panels and frame members to each other to form a preliminary loosely assembled vehicle body wherein the panels and frame members will not separate from each other but the panels and frame members can tilt or move relative to one another. This initial loosely assembled sub-assembly is then moved along the assembly line to a framing station where the various panels and frames are welded to each other to form a rigid permanently assembled vehicle body.
The welding operation step at the framing station is one of the most important steps in the assembly of the vehicle body because it establishes the final welded alignment of the various panels and headers relative to each other which is essential to subsequent assembly operations performed on the subassembly. During the welding operation it is critical that the various panels and headers be precisely and accurately located and aligned relative to one another and be held fixedly in the desired position. The positioning of the various panels and header members during the welding operation typically is accomplished by a pair of side framing gates which are positioned on opposite sides of the assembly line and which carry a plurality of individual clamps arranged thereon to clamp the various body components in desired positions.
It is desirable to perform as many welding operations as possible at the initial framing station since the relative positioning of the various panels and headers is critical to the ability to precisely relocate and reclamp the vehicle body at subsequent stations along the assembly line. Due to variations between assembly stations and variation in movement of the various panels and headers it is impossible to subsequently relocate and reclamp the vehicle body without inadvertently stacking up tolerances or creating variances between the relative positioning of various panels and headers. Therefore it is desirable to frame as much of the vehicle body as possible at the same framing station so that a maximum number of welding operations can be performed on the vehicle body without having to subsequently reclamp and relocate the vehicle body since reclamping and relocating can increase the tolerances between the relative positions of the various panels and headers of the vehicle body and decrease the repeatability between consecutive vehicle bodies in the production line.
It is common practice in the present automotive industry for one particular car model to be offered in several different body styles. Accommodating each body style requires clamping and welding different body locations as well as gaining access to different body areas so that the clamping and welding apparatus can be properly positioned while extending through the framing gates. To avoid having to provide separate assembly lines and framing stations for the different body styles of a particular car model, it is desirable to provide a single framing station that can be adapted to accommodate a plurality of different body styles in a quick and efficient manner while insuring the accuracy and repeatability that are required of the welding operation.